The relationship between the antitumor effects of NCX4040 and COX inhibition has been studied in colon cancer cells, showing that colon cancer cell lines overexpressing the COX-2 isoform were more resistant to the cytotoxic effect of NCX4040; surprisingly, in those cells exhibiting resistance to the effects of NCX4040, there was an increase in PGE2 following exposure to NCX4040 [25,26]. This evidence concerns the gene PTGS2 and colonic neoplasm.